A magnetic recording and reproducing device is mounted with a magnetic recording medium and a magnetic head, and the data on the magnetic recording medium is written in or read out by means of the magnetic head. To increase recording capacity for a unit area of the magnetic recording medium, it is necessary to increase areal recording density. However, when the bit length to be recorded becomes small, the longitudinal magnetic recording system currently practiced is apt to cause the problem of thermal fluctuation in magnetization, leading to another problem that the longitudinal recording density cannot be increased.
As a solution to the above problem, there is a perpendicular recording system in which magnetizing signal is recorded with a magnetic monopole head in the perpendicular direction onto a double-layer perpendicular medium with a soft under layer. This system makes it possible to apply a stronger recording magnetic field to a medium. Accordingly, the recording layer that has a large magnetic anisotropy constant can be used. Also, the magnetic recording medium for the perpendicular recording system has a merit in that, by making magnetic layer thicken, it becomes possible to enlarge cubic content while keeping the grain diameter appearing on the surface of the medium as small as is, that is, keeping the bit length as small as is. Further, in the perpendicular magnetic recording, record magnetization formed in the medium is kept in the direction perpendicular to the film surface, which is advantageous to stably holding record magnetization recorded in high density. With a view to enhancement of longitudinal recording density of the magnetic recording device, this perpendicular magnetic recording system is getting into wider use in place of the conventional longitudinal magnetic recording system. For the perpendicular magnetic recording, the magnetic head used for recording and reproducing is of a type of separated heads respectively for recording and reproducing. For the reproducing head, a magnetoresistance effect type head similar to the one used for conventional longitudinal magnetic recording is used, and for the recording head, a magnetic monopole head including a main magnetic pole and an auxiliary magnetic pole may be used.
In the perpendicular magnetic recording system, demand for making steeper the recording magnetic field generated by the magnetic head has arisen in order to enhance the recording characteristics such as resolution power and S/N ratio and thereby to improve track recording density and track density. However, since the magnetic flux from the main magnetic pole spreads out spatially according to the distance from the main magnetic pole, there has been a problem that the magnetic field gradient necessary for recording becomes small. Also, as the magnetic field affects adjacent tracks too, it has been regarded a problem that the data recorded in the adjacent tracks are apt to get deleted. Though effective remedy is to reduce the distance between the main pole and the medium, it is necessary on the other hand to retain a certain necessary clearance between the main pole and the medium to avoid contact with each other.
To solve the above problem, M. Mallary IEEE Trans. Magn., vol 38 pp 1719-1724 (2002) (“Non-patent Document 1”) discloses a so-called shield type magnetic monopole head in which a shield is disposed so as to absorb magnetic flux derived from the side on the trailing side of the main magnetic pole. Such shield is described as being able to make steep the head magnetic field relating to recording. Also disclosed in U.S. Pat. No. 4,656,546 (“Patent Document 1”) and Japanese Unexamined Patent Application Publication No. 2005-190518 (“Patent Document 2”) is a shield type magnetic head in which an additional shield is provided to absorb magnetic flux leaking out from the main magnetic pole to the adjacent track side. The use of this head may reduce the magnetic field charged to the adjacent tracks in the recording process.